Roseola

Roseola is most prevalent between 6 and 24 months of age and is rarely diagnosed before 3 months or after 4 years of age.

Human herpesvirus (HHV)-6B is found worldwide. Over 90% of children are seropositive for HHV-6B by 24 months of age.[1]Yamanishi K, Okuno T, Shiraki K, et al. Identification of human herpesvirus-6 as a causal agent for exanthem subitum. Lancet. 1988;1:1065-7. http://www.ncbi.nlm.nih.gov/pubmed/2896909?tool=bestpractice.com Primary infection with HHV-7 occurs at an older age than HHV-6B. About 65% of children are seropositive for HHV-7 by 36 months of age.[2]Ward KN. The natural history and laboratory diagnosis of human herpesviruses-6 and -7 infections in the immunocompetent. J Clin Virol. 2005;32:183-193. http://www.ncbi.nlm.nih.gov/pubmed/15722023?tool=bestpractice.com By adulthood >95% of patients are seropositive for HHV-6 and 85% are seropositive for HHV-7.[3]Kimberlin DW, Barnett ED, Lynfield R, et al. Human herpesvirus 6 (including roseola) and 7. In: Red Book: 2021–2024 report of the Committee on Infectious Diseases. 32nd ed. Itasca, IL: American Academy of Pediatrics; 2021. Contemporary studies show no pattern of seasonal variance.[4]Zerr DM, Meier AS, Selke SS, et al. A population-based study of primary human herpesvirus 6 infection. N Engl J Med. 2005;352:768-76. http://www.nejm.org/doi/full/10.1056/NEJMoa042207#t=article http://www.ncbi.nlm.nih.gov/pubmed/15728809?tool=bestpractice.com While more than 90% of children with primary HHV-6B infection have fever, only a minority develop classic roseola rash (reported as 23% in one study).[4]Zerr DM, Meier AS, Selke SS, et al. A population-based study of primary human herpesvirus 6 infection. N Engl J Med. 2005;352:768-76. http://www.nejm.org/doi/full/10.1056/NEJMoa042207#t=article http://www.ncbi.nlm.nih.gov/pubmed/15728809?tool=bestpractice.com Most have an undifferentiated febrile illness without rash.